Dataset for the functional assessment of animals with plant facilitation complexes

Review

A set of systematic literature searches were done in October 2014 using Web of Science with the following search terms: “plant AND facilitat* AND shrub AND insect”, “plant AND facilitat* AND shrub AND animal”, “plant AND facilitat* AND shrub AND bird” and “plant AND facilitat* AND shrub AND mammal”. Search results were refined by the “ecology” category, and there were no biases associated with publication year, journal, or article type (cursory inspection of distribution across journals and time indicated even representation). The remaining articles were compiled into a single list, and duplicates were removed providing a total of 77 primary-research publications. We then processed each individual paper in full and excluded articles that were reviews, that did not include plant-plant facilitation estimates in some form, or that did not include quantitative documentation of an interacting animal.

Findings

Facilitation studies focus primarily on plants often neglecting the extended effects that spread through ecological networks. Plants interact with other organisms through consumptive effects and a myriad of non-trophic effects such as habitat amelioration or pollination. Shrubs are a dominant benefactor species in plant facilitation studies but can also have direct and indirect effects/interactions with animals. Herein, we use a systematic review to address the following two objectives: (1) to propose a conceptual framework that explores these effects taking into consideration the functional roles of the interacting species, and (2) to formally review the current state of this field examining effects beyond the widely explored plant-plant interactions. This synthesis was explicitly structured to ensure that basal shrub-plant facilitation was included in some form with an animal species, and consequently a relatively limited number of studies have to date examined the importance of these two sets of coupled interactions (77 studies in total). From this set of studies, 34 studies documented positive plant interactions generating a total of 47 independent instances of shrub-plant-animal or shrub-animal-plant interactions. These sets of interaction pathways were relatively evenly split between direct (54%) and indirect (46%) shrub interactions with animals. Hypotheses frequently tested included seed trapping, herbivore protection, magnet pollination effects, and facilitation-mediated secondary seed dispersal. The most common functional role of shrubs was herbivore protection, and the most common animal role associated with plant-facilitation complexes was that of a consumer. However, animals also frequently provided direct positive effects including secondary seed dispersal and pollination. The implications of nested complexes of shrub-plant facilitations are thus largely unexplored particularly in their capacity to scale to other taxa or trophic levels even from the relatively simple sets of interactions summarized in this review. None of these studies explored bidirectional plant-animal interactions, used a network approach to the study facilitation, nor contrasted interaction strengths. Nested and multi-trophically integrated sets of experiments incorporating plant facilitation into community dynamics are thus critical in advancing management of high-stress ecosystems.